1. Field of the Invention
The present invention relates to a narrow width fastener tape for slide fastener composed of a warp knitting structure, and a fastener stringer in which a continuous fastener element row is attached to the fastener tape. More particularly, the invention relates to a narrow width fastener tape and a fastener stringer which have plasticity inherently possessed by a knitted fabric while its element attaching portion is difficult to stretch in a longitudinal direction and strength of the element attaching portion is intensified.
2. Description of the Related Art
In recent years, a slide fastener has been adopted by a variety of soft clothes, and thus, the plasticity of a fastener tape itself has been demanded. Then, a fastener tape composed of a warp knitting structure has been widely used from a point of view that it is more plastic than a woven fabric or the like and has an excellent stability in configuration. In general, a fastener tape of a warp knitting structure for use in a slide fastener comprises a tape main body portion to be sewed to an attachment object such as clothes and an element attaching portion to be formed along one side edge of the tape main body portion. A continuous fastener element row formed in a shape of a coil is attached to the element attaching portion by sewing.
An example of such fastener tapes for slide fastener has been described in Japanese Patent Application Laid-Open No. 55-10918, Japanese Patent No. 3439574 and the like. For example, the slide fastener tape described in the Japanese Patent Application Laid-Open No. 55-10918 has an element attaching portion (denoted as a teeth attachment area in the same document) along one side edge of a tape main body portion (denoted as an intermediate area in the same document) while an ear portion (denoted as a side edge area in the same document) is possessed on a side edge on an opposite side to the element attaching portion.
In the Japanese Patent Application Laid-Open No. 55-10918, a foundation structure of the tape main body portion is constituted of a single cord knitting yarn running across four wales and a tricot knitting yarn. A textured yarn is used as the single cord knitting yarn, and a multi-filament yarn is used as the tricot knitting yarn. Further, a chain knitting yarn composed of a multi-filament yarn is entangled in the foundation structure of the tape main body portion in the element attaching portion and the ear portion while a warp in-laid yarn composed of a multi-filament yarn is inserted in each wale in a zigzag fashion.
On the other hand, the Japanese Patent No. 3439574 discloses an invention about a fastener tape for slide fastener, in which an element attaching portion is blocked from being stretched or contracted in a longitudinal direction and a tape main body portion has a function capable of being stretched or contracted in the longitudinal direction. In a fastener tape described as an example of embodiments in the Japanese Patent No. 3439574, a foundation structure of the tape main body portion is constituted of a tricot knitting yarn composed of a multi-filament yarn and a single cord knitting yarn disposed across four wales and composed of a textured yarn. In an element attaching portion formed on one side edge of the tape main body portion, a chain knitting yarn composed of a multi-filament yarn and a warp in-laid yarn composed of a multi-filament yarn are disposed in the foundation structure of the tape main body portion.
In a fastener tape described as another embodiment in the Japanese Patent No. 3439574, a two needle stitch knitting yarn composed of a multi-filament yarn is disposed over all wales, a single cord knitting yarn composed of a textured yarn is disposed across four wales in the tape main body portion, a chain knitting yarn composed of a multi-filament yarn is disposed in the element attaching portion, and a weft in-laid yarn composed of a textured yarn is disposed across four wales with respect to the wales which constitute an element attaching portion and the tape main body portion on a side of the element attaching portion.
Further, in a wale formed on an outermost side of the element attaching portion in the above-described two kinds of fastener tapes described in the Japanese Patent No. 3439574, a chain knitting yarn thicker than chain knitting yarns disposed in other wales of the element attaching portion is disposed. Also as a knitting yarn disposed on an outermost side edge of the tape main body portion on the opposite side, a thicker knitting yarn than other knitting yarns disposed in the tape main body portion is used.
Thus, in the fastener tape of the Japanese Patent No. 3439574, an edge portion of the element attaching portion is reinforced by the thick knitting yarn, so that the fastener elements can be attached stably. Further, because the tape main body portion is composed of a knitting structure capable of being stretched or contracted, sewing means suitable for an attachment object may be used. Additionally, because the edge portion of the tape main body portion is reinforced by entangling of two kinds of thick knitting yarns, the fastener tape is prevented from being damaged and the fastener tape can be sewed to the attachment object beautifully.
On the other hand, as well as a slide fastener in which a continuous fastener element row is attached to the above-described fastener tape by sewing, there has been known a knit-in slide fastener configured such that a fastener tape is knitted using a double warp knitting machine having two columns of needle beds, and at a same time, a continuous fastener element row is attached to its element attaching portion by knitting therein. An example of the knit-in slide fastener has been described in, for example, Japanese Patent No. 3396335, Japanese Patent Application Laid-Open No. 2005-230040 and the like.
In the slide fastener described in the Japanese Patent No. 3396335, a tape main body portion is constituted of a chain knitting yarn, a tricot knitting yarn and a weft in-laid yarn to be inserted across four wales. Further, in the element attaching portion, a fixing chain knitting yarn constituted of a compact double chain knitting structure knits and fixes a fastener element row into a foundation structure constituted of a tricot knitting yarn, a weft in-laid yarn and a chain knitting yarn disposed on the outermost side of an element attaching portion.
Specifically, in the Japanese Patent No. 3396335, among a plurality of fixing chain knitting yarns, a size of the fixing chain knitting yarn near a coupling head of the fastener element is set larger than a size of the remaining fixing knitting yarns. At the same time, a needle loop of the fixing chain knitting yarn presses a tope face of an upper leg portion of an element while upper and lower leg portions of the element are tightened firmly by its sinker loop. Consequently, a tightening force and a contact area of the thickest fixing chain knitting yarn to the element are increased, so that the elements are attached strongly to the fastener tape. Further, according to the Japanese Patent No. 3396335, an attachment state of the upper and lower leg portions of the element is more stabilized, so that even when a strong bending force or push-up force is applied to a fastener surface of the slide fastener, engagement of fastener element rows can be prevented from being released.
However, when the fastener tape is knitted using the double warp knitting machine as described in the Japanese Patent No. 3396335, a stitch is formed with one needle by entangling a chain knitting yarn of a double structure, a chain knitting yarn of a single structure, a tricot knitting yarn and the like. Thus, a load applied to the needle is remarkably increased when the continuous fastener element row is fixed with a fixing knitting yarn. For this reason, breaking of the needle or skip stitch of each knitting yarn frequently occurs, which makes it very difficult to knit a fastener tape rapidly. If the leg portion on a side of a head of the element is fixed firmly with the double chain knitting yarn for fixing the element like the knit-in slide fastener described in the Japanese Patent No. 3396335, motion of the element at a time of opening/closing decreases although an engaging strength is intensified by reinforcement of the knitting yarn. Consequently, a sliding operation of a slider becomes heavy, which is an inconvenient matter to be solved.
To solve such a problem, in the knit-in slide fastener described in the Japanese Patent Application Laid-Open No. 2005-230040, basically, an element attaching portion is constituted of a foundation chain knitting yarn composed of a single structure and three or more fixing knitting yarns composed of a double structure. The fixing chain knitting yarn of the double structure constitutes a foundation structure in which a continuous fastener element row is placed such that one needle loop strides and presses over a leg portion of the continuous fastener element row while the other needle loop is entangled with a needle loop of the foundation knitting yarn.
In the knit-in slide fastener described in the Japanese Patent Application Laid-Open No. 2005-230040, both the double structure and single structure are constituted of the chain knitting structure, and further, two or more knitting yarns are not entangled in each needle. Thus, no overload is applied to the needle when the fastener tape is knitted, thereby preventing occurrence of breaking or stitch skip. Further, because according to the Japanese Patent Application Laid-Open No. 2005-230040, the double knitting yarn and single knitting yarn are knitted with the same chain knitting structure, no excessive motion is required in a knitting machine, thereby achieving a high-speed operation.
Further, because the foundation structure of the element attaching portion is constituted of the fixing chain knitting yarn and the foundation chain knitting yarn, stretching of the fastener tape in a longitudinal direction is suppressed to an appropriate extent in the element attaching portion. Additionally, because the needle loop of the fixing chain knitting yarn is disposed on both upper and lower faces of the fastener element and the fastener element is sandwiched by the sinker loop, the fastener element is tightened and fixed. Thus, the attachment strength of the fastener element row is high and a surface portion of the fastener element is soft, so that the sliding performance of the slider is improved.
In recent years, an application of the slide fastener has been expanded in diversified fields such as clothes and bags. For this reason, the slide fastener has been demanded to have a feature and function corresponding to such an application, and its fastener tape also has been demanded to possess diversified features and texture.
However, in the conventional fastener tapes, a knitted space of a knitting machine for knitting a narrow width tape is very small, and a warp knitting structure of the fastener tape is limited to a particular kind for a reason of a needle strength, so that a new feature and superiority cannot be applied to the fastener tape itself easily. For example, assuming that any knitting yarn which runs in a zigzag fashion forming the needle loop is disposed across two or more wales of the tricot knitting yarn or single cord knitting yarn at the element attaching portion of the fastener tape together with the chain knitting yarn as described in the Japanese Patent Application Laid-Open No. 55-10918 and Japanese Patent No. 3439574, the weft in-laid yarn cannot be inserted easily into the element attaching portion, so that the strength of the element attaching portion cannot be increased more than some extent.
In general, as for the slide fastener, the strength demanded for the fastener tape is increased as a size of the fastener element is increased. Therefore, because the fastener tape including no weft in-laid yarn at the element attaching portion has a limit in its strength, the size of the fastener element which can be attached is limited, which is a weak point to be solved. For this reason, the conventional fastener tapes having the single structure have not been used as a fastener tape for a slide fastener whose chain width is 7 mm or more.
If the knitting structure of the element attaching portion is constituted of the chain knitting yarn and the two needle stitch knitting yarn like the fastener tape described in the Japanese Patent No. 3439574 as another embodiment, the weft in-laid yarn can be inserted into the element attaching portion. However, in this case, nothing but a sinker loop parallel in a wale direction is formed in the chain knitting yarn and nothing but a sinker loop parallel in the wale direction and a course direction is formed in the two needle stitch knitting yarn. As a result, the element attaching portion has no sinker loop running obliquely across two or more wales between respective courses adjacent to each other like, for example, the tricot knitting yarn and single cord knitting yarn.
Thus, in a case of the fastener element as described in the Japanese Patent Application Laid-Open No. 55-10918 in which, for example, the tricot knitting yarn and the single cord knitting yarn are disposed in the element attaching portion, a lateral pulling force is applied when the slide fastener is in an engagement, for example, the element attaching portion is stretched in the width direction, and at the same time, the element attaching portion is contracted in a longitudinal direction by the sinker loops of the tricot knitting yarn or the single cord knitting yarn which run obliquely. As a consequence, an interval between respective elements of the fastener element row is narrowed, so that the engagement strength between right and left element rows is intensified. Accordingly, even when a lateral pulling force is applied to the fastener tape, the engagement of the fastener tapes can be prevented from being released.
However, if the element attaching portion is formed of the chain knitting yarn, the two needle stitch knitting yarn and the weft in-laid yarn as described in the Japanese Patent No. 3439574 as another embodiment, the element attaching portion has no sinker loop running obliquely across two or more wales between respective courses adjacent to each other like the single cord knitting yarn or the like. Thus, even if a lateral pulling force is applied to the fastener tape, the element attaching portion is not contracted in the longitudinal direction. For this reason, the engagement strength of the right and left element rows cannot be increased, and consequently, the engagement is sometimes released when the lateral pulling force is received.
On the other hand, if the element attaching portion is constituted of the double knitting structure as described in the Japanese Patent No. 3396335 and Japanese Patent Application Laid-Open No. 2005-230040, there is a problem that the plasticity inherently possessed by the knitted fabric is lost because the thickness of the element attaching portion is increased. For this reason, some measures such as forming the knitting yarn fine so as to decrease the thickness of the tape has been adopted conventionally in order to provide the fastener tape with plasticity.
In this case, however, there is such an inconvenience that the strength of the element attaching portion may drop although the plasticity of the slide fastener is secured. Strength of a material can be intensified, for example, by using a high-multi yarn as the knitting yarn at the element attaching portion in order to prevent the strength of the element attaching portion from dropping. In contrast, there exists such a problem that material cost is increased.